In his spare time Harry reads more notes in Advanced Potion-Making. The Prince seems to have been inventing spells himself, including ¤ Muffliato, a spell that fills the ears of anyone nearby with a buzzing, and a spell ¤ Levicorpus (N-vbl). Harry supposes N-vbl must mean non-verbal and doubts he will be able to perform it. Even Snape had commented on his difficulty with non-verbal spells, but the Prince had proved a much more effective teacher than Snape so far. He tries it out on Ron and Ron suddenly is dangling upside-down in midair. He quickly searches and finds the counter-jinx ¤ Liberacorpus.

Hermione thinks the Prince character a bit dodgy. Harry suddenly remembers his father used this spell, but Hermione reminds him they also saw Death Eaters use it at the Quidditch World Cup.

First trip to Hogsmeade has arrived. Slughorn presses Harry to come to his meetings, which Harry has been avoiding. In the Three Broomsticks they run into Mundungus Fletcher and catch him having a silver goblet which Harry recognizes comes from Sirius' house. Harry saw the Black family crest on it. Before Harry can do anything Mundungus Disapparates.

They decide to return to Hogwarts, following Katie Bell and one of her friends Leanne. They hear Katie having an argument with Leanne and holding something in her hand. When Leanne tries to grab the package from Katie's hand and when Katie tugs it back it falls to the floor. Katie rises in the air, arms outstretched, hair whipped around her, eyes closed. She starts to scream. When they try to pull her to the ground she already falls down and starts thrashing and screaming. He runs towards the castle to get help and runs into Hagrid. Hagrid takes her and runs off to the castle. The package on the ground contains an ornate opal necklace, Harry recognizes it being on display in Borgin and Burkes. Leanne tells them Katie came back from the bathroom in the Three Broomsticks holding it, saying it was a surprise for somebody at Hogwarts. She thinks Katie might have been Imperiused. Harry takes the necklace in his scarf back to school, they'll need to show it to Madam Pomfrey.

Harry thinks it must have been Draco who was behind it.

Professor McGonagall arrives who orders Filch to take the necklace to Dumbledore, and takes them to her office to find out what happened. Harry then accuses Draco and tells McGonagall what he had seen before. After some discussion McGonagall tells them that Draco was doing detention with her anyway, so he can't have been the one giving the necklace to Katie, and they are sent away.